Use Structured Concurrency in the Relayer

[MakMuftic]

Auditor issue

In the current state, the relayer code liberally creates goroutines whenever a background task is started.
The called function is usually passed a context so it can be canceled, but in some instances goroutines
are leaked, leading to leaked memory. It can also make it hard to keep an overview of which goroutines
are running.

Location:
Chainsafe_Sygma_Relayer/comm/p2p/libp2p.go#L81-L87
Chainsafe_Sygma_Relayer/tss/common/base.go#L119

One approach the industry developed to avoid these problems is structured concurrency. As explained in
[here] and [here], the core idea is that all goroutines must finish before the function starting them
returns.

Implementation details

We should first figure out the scope of these changes, following the proposed approach.

Testing details

TBD

Acceptance Criteria

• relayers codebase uses structured concurrency throughout the codebase